Flask



FIG. 1 is a top-front-left perspective view of a flask, showing the design;

FIG. 2 is a front view of the flask of FIG. 1;

FIG. 3 is a rear view of the flask of FIG. 1;

FIG. 4 is a right view of the flask of FIG. 1;

FIG. 5 is a left view of the flask of FIG. 1;

FIG. 6 is a top view of the flask of FIG. 1; and,

FIG. 7 is a bottom view of the flask of FIG. 1. 

CLAIM The ornamental design for a flask, as shown and described. 